Photographic emulsions stabilized with 1, 2-dithiacyclopent-3-enes



United States Patent ()1 3,114,637 PHOTOGRAPHIC EMULSIONS STABHJZED WTTH 1,2-DlCiCLOPENT-3-ENES Roy A. Jefireys, Harrow, England, assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed May 1, 1961, Ser. No. 106,524 11 Claims. (Cl. 96-109) This invention relates to stabilized photographic compositions, and more particularly, to photographic silver halide emulsions containing novel fog-inhibiting agents.

It is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation; in this invention, we are not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is, of course, desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

It is an object of this invention to provide a new method for stabilizing photographic emulsions.

It is another object of this invention to inhibit fog formation in photographic silver halide emulsions with novel addenda.

It is also an object of this invention to maintain with novel photographic addenda the sensitivity and fog of photographic silver halide gelatin emulsions at or close to initial optimum values under high temperature and igh humidity keeping conditions.

These and other objects of the invention are accomplished by incorporating into photographic silver halide emulsions stabilizing amounts of 1,2-dithiacyclopent-3-ene antifoggants having the formulas wherein R and R are inert monovalent hydrocarbon radicals, R also suitably being a hydrogen atom. R is preferably an aryl radical or an alkyl radical, with phenyl radicals including alkyl-substituted phenyl radicals being useful aryl substituents, and with alkyl radicals typically having 1 to 20 carbon atoms being useful alkyl substituents. Illustrative substituents for R include phenyl, naphthyl, tolyl, cyclohexyl, alkyl radicals having 1 to 20 Patented Dec. 17, 1963 carbon atoms and the like radicals. R can be the same substituents as described for R above or a hydrogen atom. The thione stabilizer addenda of the invention can be prepared by the method described by Bottcher and Bauer in Ann, vol. 568, page 227 (1950), and by Saudis and Hamilton in J. Org. Chem. 25, 1742 (1960). The oxime stabilizer addenda of the invention can be prepared by the method described by Voronkov, Brown, and Karpenko in Zhur. Obsh. Khim, vol. 19, page 1927 (1949).

The addenda of the invention can be added to photographic silver halide emulsions for the purpose of increasing the stability thereof. The subject addenda serve as antifoggants in photographic silver halide emulsions.

The preparation of photographic silver halide emulsions such as are suitably stabilized with the addenda of the invention typically involves three separate operations: (1) emulsification and digestion of silver halide, (2) the freeing of the emulsion of excess water-soluble salts, suitably by washing with Water, and (3) the second digestion or after-ripening to obtain increased emulsion speed or sensitivity. (Mees, The Theory of the Photographic Process, 1954.) The stabilizers of our invention can be added to the emulsion before the final digestion or after-ripening, or they can be added immediately prior to the coating.

The particular quantity of the present stabilizers used in a given emulsion can vary, depending upon the effects desired, degree of ripening, silver content of the emulsion, etc. We have found that generally from about .0001 to 5 grams per mole of silver halide are quite adequate to accomplish the desired stabilization. Exposure of the treated emulsion in conventional photographic testing apparatus, such as an intensity scale sensitometer, will reveal the most advantageous concentrations for the present stabilizers in that particular emulsion. Such techniques are well understood by those skilled in the art.

The addenda of the invention can be added to photographic emulsions using any of the well-known techniques in emulsion making. For example, they can be dissolved in a suitable solvent and added to the silver halide emulsion, or they can be added to the emulsion in the form of a dispersion similar to the technique used to incorporate certain types of color-forming compounds (couplers) in a photographic emulsion. Techniques of this type are described in Ielley et al. U.S. Patent 2,322,027, issued June 15, 1943, and Fierke et al. U.S. Patent 2,801,171, issued July 30, 1957. The solvent should be selected so that it has no harmful effect upon the emulsion in accordance with usual practice, and generally solvents or diluents which are miscible with water are to be preferred. Water alone is a dispersing medium for some of the stabilizers of the invention. In other cases, the subject stabilizers can be dissolved in solvents, such as ethanol, acetone, pyridine, N,N-dimethylformamide, etc., and added to the emulsion in this form.

The emulsions of the invention can be chemically sensitized by any of the other well-known procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added, such as those described in Sheppard U.S. Patent 1,574,944, issued March 2, 1926, and Sheppard et al. 1,623,499, issued April 5, 1927, and Sheppard and Brigham U.S. Patent 2,410,689, issued November 5, 1946. The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245, issued August 28, 1951, and 2,566,263, issued August 28, 1951. The emulsions can also contain sensitizing amounts of gold salts as de scribed in Waller et al. U.S. Patent 2,399,083, issued April 23, 1946, or stabilizing amounts of gold salts as described in Damschroder U.S. Patent 2,597,856, issued May 27, 1952, and Yutzy and Lcermakers U.S. Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride. The emulsions can also contain sensitizing amounts of reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850, issued November 15, 1949), polyamines, such as diethylene triamine (Lowe and Jones U.S. Patent 2,518,698, issued August 15, 1950), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12, 1950), or bis(fiaminoethyl)sulfide and its water-soluble salts (Lowe and Jones U.S. Patent 2,521,926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker U.S. Patents 1,846,301, issued February 23, 1932; 1,846,302, issued February 23, 1932; and 1,942,854, issued January 9, 1934; White U.S. Patent 1,990,507, issued February 12, 1935; Brooker and White U.S. Patents 2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950; and 2,739,- 964, issued March 27, 1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950; Sprague U.S. Patents 2,503,776, issued April 11, 1950, and 2,519,001, issued August 15, 1950; Heseltine and Brooker U.S. Patent 2,666,761, issued January 19, 1954; Heseltine U.S. Patent 2,734,900, issued February 14, 1956; Van Lare U.S. Patent 2,739,149, issued March 20, 1956; and Kodak Limited British Patent 450,958, accepted July 15, 1936.

The emulsions can also contain speed-increasing compounds of the quaternary ammonium type of Carroll US. Patent 2,271,623, issued February 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June 30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued November 23, 1943; and the polyethylene glycol type of Carroll and Beach U.S. Patent 2,708,162, issued May 10, 1955.

The emulsions can contain a suitable gelatin plasticizer such as glycerin; a dihydroxy alkane such as 1,5-pentane diol as described in Milton and Murray U.S. Patent 2,960,- 404, issued November 15, 1960; an ester of an ethylene bis-glycolic acid such as ethylene bis(methyl glycolate) as described in Milton U.S. Patent 2,904,434, issued September 15, 1959; bis(ethoxy diethylene glycol) succinate as described in Gray U.S. Patent 2,940,854, issued June 14, 1960, or a polymeric hydrosol as results from the emulsion polymerization of a mixture of an amide of an acid of the acrylic acid series, an acrylic acid ester and a styrene-type compound as described in Tong U.S. Patent 2,852,386, issued September 16, 1958. The plasticizer may be added to the emulsion before or after the addition of a sensitizing dye, if used.

The emulsion can be hardened with any suitable hardener for gelatin such as formaldehyde; a halogen-substituted aliphatic acid such as mucobromic acid as described in White U.S. Patent 2,080,019, issued May 11, 1937; a compound having a plurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,2)-7-octene-2,3,5,6-tetracarboxylic dianhydride, or a dicarboxylic or a disulfonic acid chloride such as terephthaloyl chloride or naphthalene-1,5-disulfonyl chloride as described in Allen and Carroll U.S. Patents 2,725,294 and 2,725,295, both issued November 29, 1955; a cyclic 1,2-diketone such as cyclopentane-1,2-dione as described in Allen and Byers U.S. Patent 2,725,305, issued November 29, 1955; a bisester of methane-sulfonic acid such as 1,2-di-(methanesulfonoxy)ethane as described in Allen and Laakso U.S. Patent 2,726,162, issued December 6, 1955; 1,3-dihydroxymethylbenzimidazol-Z-one as described in July, Knott, and Pollak U.S. Patent 2,732,316, issued January 24, 1956;

a dialdehyde or a sodium bisulfite derivative thereof, the aldehyde groups of which are separated by 23 carbon atoms, such as fl-methylglutaraldehyde bis-sodium bisullite; a bisaziridine carboxamide such as trimethylene bis( 1- aziridine carboxamide) as described in Allen and Webster U.S. Patent 2,950,197, issued August 23, 1960; or 2,3- dihydroxy dioxane as described in Jeffreys U.S. Patent 2,870,013, issued January 20, 1959.

The emulsion can contain a coating aid such as saponin; a lauryl or oleoyl monoether of polyethylene glycol as described in Knox and Davis U.S. Patent 2,831,766, issued April 22, 1958; a salt of a sulfated and alkylated polyethylene glycol ether as described in Knox and Davis U.S. Patent 2,719,087, issued September 27, 1955; an acylated alkyl taurine such as the sodium salt of N-oleoyl-N-methyl taurine as described in Knox, Twardokus, and Davis U.S. Patent 2,739,891, issued March 27, 1956; the reaction product of a dianhydride of tetracarboxybutane with an alcohol or an aliphatic amine containing from 8 to 18 carbon atoms which is treated with a base, for example, the sodium salt of the monoester of tetracarboxybutane as described in Knox, Stcnberg, and Wilson U.S. Patent 2,843,487, issued July 15, 1958; a water-soluble maleopimarate or a mixture of a watensoluble maleopimarate and a substituted glutamate salt as described in Knox and Fowler U.S. Patent 2,823,123, issued February 11, 1958; an alkali metal salt of a substituted amino acid such as disodium N-(carbo-p-tert.octylphencxypentaethoxy)glutamate, or a sulfosuccinamate such as tetrasodiurn N-(1,2- dicarboxyethyl)-N-octadecyl sulfosuccinamate, or N- lauryl disodium sulfosuccinamate.

The stabilizer addenda of the invention can be used in various kinds of photographic emulsions. In addition to being useful in orthochromatic, panchromatic, and infrared sensitive emulsions, they are also useful in X-ray and other non-optically sensitized emulsions. They can be added to the emulsion before or after any optical sensitizing dyes which may be used. Various silver salts can be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide or silver bromoiodide. The subject addenda can be used in emulsions intended for color photography, for example, emulsions containing colorforrning couplers or emulsions to be developed by solutions containing couplers or other color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky U.S. Patent 2,698,794, issued J anuary 4, 1955, or emulsions of the mixed-grain type, such as described in Carroll and Hanson U.S. Patent 2,592,243, issued April 8, 1952. The subject stabilizers can also be used in emulsions which form latent images predominantly on the surface of the silver halide crystal or in emulsions which form latent images predominantly inside the silver halide crystal, such as those described in Davey and Knctt U.S. Patent 2,592,250, issued April 8, 1952.

The subject addenda can also be used in emulsions intended for use in diffusion transfer processes which utilize the undeveloped silver halide in the non-image areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in Rott U.S. Patent 2,352,014, issued June 20, 1944, and Land U.S. Patents 2,584,029, issued January 29, 1952; 2,608,236 issued December 28, 1954 and 2,543,181, issued February 27, 1951. They can also be used in color transfer processes which utilize the diffusion transfer of an imagewise distribution of developer, coupler or dye, from a light-sensitive layer to a second layer, while the two layers are in close proximity to one another. Color processes of this type are described in Land U.S. Patents 2,559,643, issued July 10, 1951, and 2,698,798, issued January 4, 1955; Land and Rogers Belgian Patents 554,933 and 554,934, granted August 12, 1957; International Polaroid Belgian Patents 554,212,

granted July 16, 1957, and 554,935, granted August 12, 1957; and Yutzy US. Patent 2,756,142, issued July 24, 1956.

In the preparation of the silver halide dispersions em ployed for preparing silver halide emulsions, there can be employed as the dispersing agent for the silver halide in its preparation, gelatin or some other colloidal material such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound, although gelatin is preferred. So-me colloids which can be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe US. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19- 26% as described in US. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy U.S. Patent 2,322,085, issued June 15, 1943; a polyacrylarnide having a combined acrylamide content of 30-60% and a specific viscosity of 025-15 on an irnidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk, and Kenyon US. Patent 2,541,474, issued Feb ruary 13, 1951; zein as described in Lowe US. Patent 2,563,791, issued August 7, 1951; a vinyl alcohol polymer containing urethane ca-rboxylic acid groups of the type described in Unruh and Smith US. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate oopolymer as described in Unruh, Smith, and Priest US. Patent 2,808,331, issued October 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in I'llingsworth, Dann, and Gates U.S. Patent 2,852,382, issued September 19, 1958. If desired, compatible mixtures of two or more of these colloids can be employed for dispersing the silver halide in its preparation.

The above-described emulsions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include cellulose nitrate film, cellulose acetate fi'l-m, polyvinyl acetal film, polystyrene film, polyethyleneterephthalate film and related films of resinous materials, as well as glass, paper, metals and others.

The invention is further illustrated by the following examples of preferred embodiments thereof.

EXAMPLE 1 Typical stabilizers of the invention were incorporated into a high speed, negative-type gelatino-silver bromoiodide emulsion which was panchromatically sensitized with a cyanine dye. The silver halide comprising the pre pared photographic emulsions was prepared from 56 grams of silver nitrate per liter of emulsion. The emulsions were coated on cellulose acetate film supports. The prepared photographic elements were then exposed, after 3 month and 6 month intervals of storage under ambient conditions, in the form of film strips in an Eastman type Ib sensitometer, developed for five minutes at 68 F., and then fixed, washed and dried in the usual manner. Test samples were also exposed directly after coating in the sensitorneter for purposes of comparison. The developer had the following formula:

Water to make one liter.

The results of the sensitometric tests are summerized by the data set out in Tables A and B below with respect to the relative speed and fog for the various samples. In Tables A and B the speeds indicated are a function of the exposure necessary to give a density of 0.2 above background fog, the initial control speed being taken as 100 in each case; and the concentrations of addenda are indicated as grams of addenda per mole of silver halide.

Table A Cone. of Initial 3 Months 6 Months Addenda Test Aiter After Addenda (grams! Coating Coating mole of X) Speed Fog Speed Fog Speed Fog Control 100 0.16 0.16 80 0.18 Compound 1" .00045 100 0.12 0.09 80 0.15 Compound 1 .0018 90 0.12 85 0.07 80 0.12

'3-pheny1-1,2-dithiaeyclopent-ilen-fi-thione.

Table B Cone. of Initial 3 Months 6 Months Addenda Test After After Addenda (grams Coating Coating mole of AgX) Speed Fog Speed Fog Speed Fog Control 100 0.11 100 0.13 0.18 Compound 2* 0027 80 0.09 0.08 95 0.14

*3-phenyl -1,2dithiacyelopent-3-en-5-0xime. As can be observed from the data set out in Tables A and B, the addenda of the invention substantially stabilized the photographic silver halide emulsions, and in particular, these addenda were demonstrated to be useful antifoggants.

EXAMPLE 2 Samples of the photographic emulsion described in Example 1 were tested with another stabilizer of the invention. The emulsions were coated and exposed in a sensitometer as described in Example 1 after being subjected for 7 days to a relative humidity of 42% and a temperature of F. Test samples were also exposed directly after coating in the sensitometer for purposes of comparison. The results of the sensitometric tests are summarized by the data set out in Table C below wherein the speeds indicated are a function of the exposure necessary to give a density of 0.2 above background fog, the initial speed being taken as 100 in each case; and the concentrations of addenda are indicated as grams of addenda per mole of silver halide.

*3-tert.butyl-4-neopentyl-1,2-dithiaeyelopent-B-en-thione.

The data in Table C further illustrate the stabilizing properties of the subject addenda in photographic silver halide emulsions.

The present invention thus provides a new and useful class of photographic silver halide emulsion stabilizing addenda.

Although the invention has been described in detail with reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined by the appended claims.

I claim:

1. A photographic silver halide emulsion containing a stabilizer having a farmula selected from the group consisting of wherein R is selected from the group consisting of an alkyl radical and an aryl radical and R is selected from the group consisting of a hydrogen atom, an alkyl radical and an aryl radical.

2. A photographic silver halide stabilizer having the formula c=s s s wherein R is selected from the group consisting of an alkyl radical and an aryl radical and R is selected from the group consisting of a hydrogen atom, an alkyl radical and an aryl radical.

3. A photographic silver halide stabilizer having the formula emulsion containing a emulsion containing a wherein R is selected from the group consisting of an alkyl radical and an aryl radical and R is selected from the group consisting of a hydrogen atom, an alkyl radical and an aryl radical.

4. A photographic gelatino-silver halide emulsion containing a 3-aryl-1,2-dithiacyclopent-3-en-5-thione stabilizer.

5. A photographic gelatino-silver halide emulsion containing a 3-aryl-1,2-dithiacyclopent-3-en-5-oxime stabilizer.

6. A photographic gelatino-silver halide emulsion containing a 3-4-dialkyl-1,2-dithiocyclopent-3-en-5-thione stabilizer wherein the alkyl radicals each have 1 to 20 carbon atoms.

7. A photographic gelatino-silver halide emulsion containing a 3,4-dialkyl-1,2-dithiocyclopent-3-en-5-oxime stabilizers wherein the alkyl radicals each have 1 to 20 carbon atoms.

8. A photographic gelatino-silver brornoiodide emulsion containing about .0001 to 5 grams per mole of silver bromoiodide of 3-phenyl 1,2 dithiacyclopent 3-en-5- thione.

9. A photographic gelatino-silver bromoiodide emulsion containing about .0001 to 5 grams per mole of silver bromoiodide of 3-phenyl 1,2 dithiacyclopent 3-en-5- oxirne.

10. A photographic gelatino-silved bromoiodide emulsion containing about .0001 to 5 grams per mole of silver bromoiodide of 3-tert.butyl-4-neopentyl-1,2-dithiacyclopent-3-en-5-thione.

11. A photographic emulsion support having coated thereon a photographic silver halide emulsion as described in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,438,716 Mueller Mar. 30, 1948 2,705,680 Jarvi Apr. 5, 1955 2,948,614 Allen et al Aug. 9, 1960 3,043,696 Herz et a1 July 10. 1962 OTHER REFERENCES I. Organic Chemical 25, 1742-1744, 1960 (copy in Sci. Lib.). 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING A STABILIZER HAVING A FARMULA SELECTED FROM THE GROUP CONSISTING OF 